8. Windows and exterior doorways in existing dwellings and outbuildings

Roof window and ranch slider

A building consent is usually not required for building work related to a window or exterior doorway in an existing dwelling.

What the law says

Subject to section 42A of the Building Act, Schedule 1 exempts the following from a building consent:

Building work in connection with a window (including a roof window) or an exterior doorway in an existing dwelling that is not more than 2 storeys or in an existing outbuilding that is not more than 2 storeys, except:

(a) in the case of replacement, if the window or doorway being replaced has failed to satisfy the provisions of the building code for durability, for example, through a failure to comply with the external moisture requirements of the building code; or
(b) if the building work modifies or affects any specified system.

Guidance on the exemption

This exemption allows you to carry out any building work in connection with a window (including a roof window, whether it is fixed or opening) or an exterior doorway without needing a building consent where it is an existing dwelling or outbuilding.

That is as long as the original doorway or window has not failed prematurely and replacing it will not modify or affect any specified system (eg sprinklers or fire alarms).

If you are replacing a window, roof window or door, it is important to consider whether it originally met the durability requirements of the Building Code. In most cases, doors and windows in an external wall are required to last at least 15 years. Most windows and doors should achieve this requirement with regular maintenance.

If the door or window is older than 15 years and you are replacing it because it has rotted out, then this work will not require a building consent.

However, if you are replacing a window, roof window or door that has been installed within the last 15 years and it has failed (eg it has rotted out), this work will require a building consent. This recognises that replacing a window or door that has failed its durability requirements with a similar window or door could result in the replacement also failing.

All new building work must comply with the Building Code, including the structural performance requirements. Also note that, on completion of the building work, the altered building must comply with the Building Code to at least the same extent as it did before the building work was undertaken.

Load-bearing walls

If you are considering building work that is close to or involves potentially load-bearing walls, it is important to get professional advice (eg from a chartered professional engineer, registered architect, building consultant or registered building surveyor).

Examples where this exemption could apply

Installing a roof window to an upper level apartment of a 2 storey multi-unit dwelling (ie an apartment building). The skylight will be installed between the existing roof trusses without altering any specified systems.
A home owner decides to replace a damaged, non fire-rated window that is 500 mm from the boundary. As the replacement window is within a metre of the boundary and as the new building work must comply with the Building Code, the window must provide adequate protection to the boundary (it could either be a fire-rated window or a non fire-rated window which is suitably protected; eg by a drencher system). The existing windows (which are non fire-rated) in the same wall can remain because the house still complies to the same extent as it did before the alteration (refer to section 42A(2)(b)(ii) of the Building Act).
Removing a dwelling’s lounge window and covering the opening with external cladding and internal linings to form a wall with no opening. Note that minimum Building Code requirements will still need to be met for ventilation, natural light and visual awareness of the outside environment.
Following earthquake damage, a builder decides to install a bi-fold door to replace a pair of French doors leading from the ground floor dining room of a 2 storey dwelling. As the wall opening for the new joinery is wider than the existing opening, he needs to install a new lintel to span the opening.
To gain more sunlight, a home owner decides to install a window in an external fire-rated bedroom wall which contains no other openings. As the window will be less than 1 metre from the boundary, the owner instructs the builder to install a fire-rated window to meet the Building Code requirements.

Examples where building consent is required

A window installed in an existing outbuilding only six years ago needs to be replaced because of a rotten timber window frame. Replacing this window requires a building consent because it has failed its 15 year durability requirement.
The owner of a commercial building wants to install a roof window into an existing roof and ceiling to a top floor office. As this building is not a dwelling or outbuilding and as the roof window installation will affect the existing sprinkler system, a building consent is required.

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This information is published by the Ministry of Business, Innovation and Employment’s Chief Executive. It is a general guide only and, if used, does not relieve any person of the obligation to consider any matter to which the information relates according to the circumstances of the particular case. Expert advice may be required in specific circumstances. Where this information relates to assisting people: